The present invention relates to a semiconductor device including a storage device, and more particularly relates to the configuration of a circuit for reading data stored in the storage device.
A sense amplifier is used as a circuit for reading data stored in a storage device. The sense amplifier detects a very small potential difference between two opposite bit lines and evaluates the detected difference to "0" or "1" in order make the read speed high.
From the point of view of power consumption, the storage device reading circuit is not suitable for low speed reading operation while it is suitable for high speed reading operation. This is because the power consumed by the sense amplifier is the dominant power consumption during low speed reading operation, while the power consumed by the sense amplifier is not so large in comparison with the power consumed in the storage device during high speed reading. If a conventional circuit for reading a storage device is applied to, for example, a micro-computer system having two, high and low speed central processing unit (CPU) clocks, very much power is consumed by a sense amplifier even in the case of access to the storage device with the low speed clock.